Giải bài 4 trang 18 vở thực hành Toán 7

Đề bài

Bỏ dấu ngoặc rồi tính các tổng sau:

a, \(\frac{{17}}{{11}} - \left( {\frac{6}{5} - \frac{{16}}{{11}}} \right) + \frac{{26}}{5};\)

b, \(\frac{{39}}{5} + \left( {\frac{9}{4} - \frac{9}{5}} \right) - \left( {\frac{5}{4} + \frac{6}{7}} \right).\)

Lời giải chi tiết

a, \(\frac{{17}}{{11}} - \left( {\frac{6}{5} - \frac{{16}}{{11}}} \right) + \frac{{26}}{5}\)

 \(\begin{array}{l}= \frac{{17}}{{11}} - \frac{6}{5} + \frac{{16}}{{11}} + \frac{{26}}{5}\\ = \left( {\frac{{17}}{{11}} + \frac{{16}}{{11}}} \right) + \left( {\frac{{26}}{5} - \frac{6}{5}} \right)\\ = \frac{{33}}{{11}} + \frac{{20}}{5}\\ = 3 + 4\\ = 7.\end{array}\)

b, \(\frac{{39}}{5} + \left( {\frac{9}{4} - \frac{9}{5}} \right) - \left( {\frac{5}{4} + \frac{6}{7}} \right) \)

\(\begin{array}{l}= \frac{{39}}{5} + \frac{9}{4} - \frac{9}{5} - \frac{5}{4} - \frac{6}{7}\\ = \left( {\frac{{39}}{5} - \frac{9}{5}} \right) + \left( {\frac{9}{4} - \frac{5}{4}} \right) - \frac{6}{7}\\ = \frac{{30}}{5} + \frac{4}{4} - \frac{6}{7}\\ = 6 + 1 - \frac{6}{7} = \frac{{49}}{7} - \frac{6}{7}\\ = \frac{{43}}{7}.\end{array}\)